Vacuum drying cabinet



June l4, 1955 A. L. ANDERSEN 2,710,456

V vacuum DRYING CABINET Filed Aug. 2. 1951 II/a lIIIIIII/I 20- I mvz-rmale. Auosns Lnumos AHDERSEII VACUUM DRYING CABINET Anders Laurids Andersen, Taastrup, near Copenhagen, Denmark Application August 2, 1951, Serial No. 239,935

2 Claims. (Cl. 3492) The present invention relates to vacuum drying cabinets.

It is the particular object of the invention to provide a drying cabinet in which mild but nevertheless quick drying of delicate materials may be carried out, for instance of materials for use in the production of medicinal goods. To achieve this object the drying cabinet and its appurtenant trays are so arranged that the materials resting on the'trays are exposed to heat by radiation from above and also to heat from heating elements placed in the bottoms of the trays, particularly a steam-jacket covering the bottom of the tray, while at the same time the space in which the tray is placed is connected with a vaccum so that the vapour from the drying goods will rapidly be drawn 01f.

In order that the drying cabinet may be kept working continuously it would be expedient to have it subdivided into several compartments each with a front door, ceiling, floor, sidewalls and rear wall so that the trays may be removed from one compartment while the other compartments of the cabinet continue in operation.

Each drying tray is provided with a pipe connection which when the tray is pushed in on the brackets arranged on the sidewalls of the cabinet will enter into a delivery pipe for hot steam which thus will enter the steam-jacket and heat the bottom of the drying tray. The condensate formed is in a simple manner made to flow out into the cabinet through a drain pipe connected with the steam-jacket and open to the cabinet. It is one of the objects of the invention to provide reliable drainage of the condensate formed in the steam-jacket of the tray and to ensure that any condensate left in the tray does not flow out when the tray is removed. It is a further object of the invention to ensure that the condensate from the drain pipe is carried directly to the vacuum pipes leading from the cabinet, so that the quickest possible removal of the condensate will be ensured.

This object is attained according to the invention by the drain pipe opening in a sump in the steam-jacket, so that the maximum amount of water collected in the jacket will be drawn ofi through the pipe, while at the same time the cabinet is provided with a vacuum pipe connection which through a pipe is connected with the source of vacuum in the immediate proximity of the drain pipes when the drying tray is in place in the cabinet.

It is a further object of the invention to provide the steam necessary for the heating of the cabinet in a simple manner. This object is attained by the use of a steam generator which through a pipe provided with valves is connected with the pipe branches supplying steam to the pipes of the drying trays. Thereby, when the trays are in place an open connection will be formed from the vacuum through the vacuum branch pipes opening in the cabinet to the steam-jackets of the trays and thence through the branch pipes and connecting pipes to the steam generator in the steam space of which a very low pressure will thus be created, so that the steam delivered sited States Fatent fitice by the generator will have a low temperature corresponding to the low pressure. By correct adjustment a very mild but at the same time rapid drying will be obtained.

With the above objects in view the present invention mainly comprises a drying tray device for insertion into a vacuum drying cabinet having at least one compartment into which open pipes connected, respectively, with a vacuum producing means and a steam generator, the cabinet department having support brackets therein, the tray device comprising, in combination, a tray portion open at its top, a steam jacket covering at least the entire bottom of the tray portion, the steam jacket being formed with a sump, supporting members for supporting the tray portion and steam jacket on the support brackets in the cabinet compartment, a supply branch pipe connected to the steam jacket of the tray portion for supplying steam to the steam jacket, the branch pipe being adapted to be connected with the steam supply pipe opening into the cabinet compartment when the drying tray device is inserted into the cabinet compartment and resting on the support brackets, and an upwardly extending spout connected at its lower end to the sump in the steam jacket and opening at its upper end into the cabinet compartment.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 shows a drying tray device inserted into a vacuum drying cabinet in side elevation with part of the sidewall removed,

Fig. 2 shows a drying tray being inserted into a vacuum drying cabinet in front View with part of the front wall removed, partly in cross-section;

Fig. 3 shows on an enlarged scale in cross-section part of the tray with a sump portion formed therein, as illustrated in Fig. 2; and

Fig. 4 shows a cross-section taken along line IVIV of Fig. 3.

In the embodiment shown the cabinet consists of a casing 1, which by a horizontal partition 2, is divided into two compartments each of which is provided with a front door 3 and otherwise has two sidewalls 4, a ceiling 5, and a rear wall 6. The ceilings 5 of each compartment are provided with heat elements 7 which in the embodiment shown consist of steam coils receiving steam from a steampipe 8, which by a supply pipe 9, is connected with a steam generator not shown in the drawmg.

The sidewalls are provided with support brackets 10 for the drying trays which rest on these brackets 10 by supporting members 11 which in the embodiment shown consist of rollers on which the trays may be run into and out of the cabinet. Each compartment is further in way of the brackets It} provided with branch pipes 12 for the supply of steam. These branch pipes are by pipelines 13 with valves 14 and 15 connected with pipes 16 leading to a steam generator 17. Pipe 16 is provided with a manometer 38 and a thermometer. 39 in order that pressure and temperature of the steam leaving the generator may be controlled.

The steam generator is provided with a heating element 18 which in the embodiment shown consists of steam pipes which through a hand operated valve 19, and an automatic valve 21 provided with a thermoregulator 20 is supplied with steam from pipe 9.

Each compartment is further provided with a plurality of vacuum branch pipes 22 arranged, respectively, at a short distance above the brackets 10. In the embodiment shown each compartment has three sets of brackets, so that three drying trays may be inserted in the compartment. As a consequence there are also three vacuum branch pipes 22 which through a pipe 23 provided with suitable valves are connected with a vacuum source. On pipes 23, vacuum meters 24 are inserted.

The drying trays or tray portions 25 running on the brackets are open at top. In their bottoms they are provided with steam-jackets 26 with a pipe connection 27 which when the tray is inserted with its supporting members 11 resting on the brackets 10 will enter thebranch pipes 12 which are provided with rings 28 so that the tray will be in steamtight connection with branch pipe 12 when inserted in the compartment.

Each steam-jacket 26 is further provided with a drain pipe 29 opening openly into the cabinet through a spout 30 with a small hole. The drain pipe opens in a sump 31 in the tray and is on its outside carried upwards so as to form a syphon. The longitudinal line passing through steam jacket 26, as shown in Fig. 3, indicates part of the wall defining sump 31, which as shown in Fig. 4 extends below the bottom of the steam jacket 26.

In the embodiment shown the drying cabinet 1, with all its appurtenant parts, is placed on top of the steam generator 17 so that the cabinet and the steam generator form one unit.

In front of the drying cabinet an elevator is arranged, consisting of a standard 32 with a motordriven mechanism 33 by means of which an elevator 34 may be raised and lowered. The elevator is provided with a rotatable platform 35 on which the trays may be placed when they are to be inserted into or removed from the cabinetgthe elevator being first raised or lowered to a suitable level, and when the tray has been placed on the platform, the latter may be swung into a convenient position.

The steam generator 17 is provided with a safety valve 36, and the vacuum pipes 23 with a vent 37.

The drying cabinet operates as follows: Heating elements 7 and 18 are started with all valves closed. The material to be dried is then placed in the trays which are placed on platform 35 in horizontal position and then raised to the level of the brackets 10 on which the tray is to be placed. The tray is then inserted into place, so that its branch pipe 27 enters the branch pipe 12. Thereafter the valves 15 are opened in those branch pipes 13 which correspond to the brackets on which drying trays have been inserted. When the entire compartment has been filled up the front door 3 is closed. Then pipes 23 are opened so that a vacuum will be created in the cabinet.

As the ceiling 5 is'heated by the heating element 7 'heat will radiate from the ceiling to the uppermost drying tray 25. The steam from the steam generator 17 will heat the steam-jackets 26 so that they will transmit heat partly direct to the materials lying in the tray, and partly by radiation to the tray underneath. The steam entering steam-jacket 26 will be condensed and flow into sump 31. As the drain pipe 29 opens direct into the cabinet by way of the corresponding vacuum pipe 22 the condensate accumulated in the sump will be sucked out through pipe 29 and flow straight into the pipe 23 leading to the vacuum pump. At the same time the vacuum prevailing in the cabinet will be transmitted through the drain pipe 29 to the steam-jacket 26 and thence through pipe branches 27 and 12 to pipe 16 to the generator 17 so that the pressure therein will be less than 1 at. Consequently 'the steam emanating from the generator will be of low temperature.

When drying has been completed the steam supply from the generator 17 is shut 0E, and then connections to the vacuum are closed, whereupon the air vent 37 is opened so that the front door 3 may be opened. When the trays are removed any water remaining in the steamjacket 26 will not be spilled out through the drain pipe 29, the latter being formed as a syphon.

The invention is not confined to heating of particularly the generator 17 and the heating element 7 by steam, as other heating media, especially electricity may be used for this purpose.

Further, it may be pointed out that it may be expedient instead of constantly-open drain pipes 29, to use pipes which in the same manner as water separators are provided with an automatic valve which opens when cold and closes when Warm.

What I claim is:

1. A drying tray device for insertion into a vacuum drying cabinet having at least one compartment into which open pipes connected, respectively, with a vacuum producing means and a steam generator, the cabinet compartment having support brackets therein, said tray device comprising, in combination, a tray portion open at its top; a steam jacket covering at least the entire bottom of the tray portion, said steam jacket being formed with a sump; supporting members for supporting said tray portion and steam jacket on the support brackets in the cabinet compartment; a supply branch pipe connected to said steam jacket-of said tray portion for supplying steam to said steam jacket, said branch pipe being adapted to be connected with.the steam supply pipe opening into the cabinet compartment when the drying tray device is inserted into the cabinet compartment and resting on the support brackets; and an upwardly extending spout connected at its lower end to said sump in said steam jacket and opening at its upper end into the cabinet compartment.

2. A drying tray device for insertion into a vacuum drying cabinet having at least one compartment into which open pipes connected, respectively, with a vacuum producing means and a steam generator, the cabinet compartment having support brackets therein, said tray device comprising, in combination, a tray portion open at its top; a steam jacket covering at least the entire bottom of. thetray portion, said steam jacket being formed with a sump; supporting members for supporting said tray portion and steam jacket on 'the support brackets in the cabinet compartment; a supply-branch pipe connected to said steam jacket of said tray portion for supplying steam to saidsteam jacket, said branch pipe being adapted to be connected with the steam supply pipe opening into the cabinet compartment when the drying tray device is inserted into the cabinet compartment and resting on the support brackets; and an upwardly extending spout connectedat its lower end to-said sump in said-steam jacket and opening at its upper end into the cabinet compartment, said upwardly extending spout being arranged so as to discharge into'the'pipe connected to the vacuum producing means, said spout thereby serving as a siphon through which condensate accumulating in said sump is lenaove'd-throu'ghthe pipe connected to the vacuum producing means.

"References Cited in the file of this patent UNITED STATES PATENTS 

